Silicon Image SSD-H16G(I)-3500 manual Drive/Head Register, LBA27 LBA26 LBA25 LBA24

ATA REGISTERS SSD-HXXX(I)-3500 DATA SHEET

DRIVE/HEAD REGISTER

The Drive/Head register is used by the host and the device to select the type of addressing (CHS or LBA), the drive letter, and either bits 3-0 of the head number in CHS mode or logical block number bits 27-24 in LBA mode.

Table 24: Drive/Head Register

Operation	D7	D6	D5	D4	D3	D2	D1	D0
Read/Write	1	LBA	1	DRV	HS3	HS2	HS1	HS0
					LBA27 LBA26 LBA25 LBA24
Default	1	0	1	0	0	0	0	0
Value

The Drive/Head register is used by the host to specify one of a pair of ATA drives present in the platform.

Bit(s)	Description
6	LBA. Selects between CHS (0) and LBA (1) addressing mode.

4Drive Address (DRV). Indicates the drive number selected by the host, either 0 or 1.

3-0 HS3 to 0. Indicates bits 3-0 of the head number in CHS addressing mode or LBA bits 27-24 in LBA mode.

•CHS to LBA conversion: LBA = (C x HpC + H) x SpH + S -1

•LBA to CHS conversion:

C = LBA/(HpC x SpH)

H = (LBA/SpH) mod (HpC)

S = (LBA mod(SpH)) + 1

...where:

C is the cylinder number H is the head number S is the sector count

HpC is the head count per cylinder count SpH is the sector count per head count (track)

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3500H-03DSR PAGE 22 FEBRUARY 2, 2009